When power transistors which are used to supply a voltage to a load are switched on and off, there is on the one hand the aim, in order to avoid switching losses, of keeping the switching processes, that is to say the transitional phases between the two switching states, as short as possible. On the other hand, steep switching flanks of the voltage across the power transistor and of the current flowing through the power transistor should be avoided in order to reduce electromagnetic interference radiation that occurs during the switching processes.
The switching processes can be optimized taking account of these two conditions by a gate electrode of the power transistor being charged with a different control current before a gate-source voltage reaches the value of the threshold voltage of the transistor, in the same way as after this threshold voltage is reached.
A drive such as this requires information about the value of the threshold voltage of the power transistor. However, this threshold voltage is governed by the production process for the power transistor and, furthermore, is subject to a not-inconsiderable process-dependent scatter, and is dependent on the temperature. The storage of information about the threshold voltage in the drive circuit is therefore impossible at the manufacturer, or is possible only with considerable complexity.